Start-up fuel injection system

ABSTRACT

A start-up fuel injection system for an internal combustion engine providing an enriched air-fuel mixture during start-up and warming-up by a solenoid valve controlled injector system. The solenoid valve is energized in dependence on a signal produced by a combination of actions of a thyristor and a thermistor or a combination of similar basic elements.

O United States Patent [151 3,704,702

Aono 1 Dec. 5, 1972 [54] START-UP FUEL INJECTION SYSTEM [56] References Cited Inventor: Aono, YOkOSllka, Japan [731 Assign Nisan Company, PiFF 3,533,381 10/1970 Schmid et al. ..123/179 0 x YkhamaJaPm 3,456,628 7/1969 Bassot et al.... ....123/119 R x [22] Filed: Oct. 19, 1970 3,490,425 1/1970 Bassot et al. ....123/1 19 R X [211 pp No: ,8 3 3,587,553 6/1971 Sutton ..l23/l79 G X Primary Examiner-Laurence M. Goodridge [30] Foreign Application Priority Data Attorney-John Lezdey Oct. 22, 1969 Japan ..44/84432 [57] ABSTRACT [52] US. Cl. ..l23ll79 G, 123/32 AE, 123/180 T, A start-up fuel injection system for an internal com- 123/ 187.5 R bustion engine providing an enriched air-fuel mixture [51] Int. Cl ..F02n 17/00 during start-up and warming-up by a solenoid valve [58] Field of Search ..l23ll19 R, 179 G, 187.5 R, controlled injector system. The solenoid valve is ener- 123/180 T gized in dependence on a signal produced by a combination of actions of a thyristor and a thermistor or a combination of similar basic elements.

3 Claims, 3 Drawing Figures PATENTEDnEc 5 I972 3.704,?02

A SHEEI 1 BF 2 INVENTOR SIl/GE 0 50 1 BY ATTOR PATENTED IIEIJ 5 I972 3 7 04 i 7 O 2 sum 2 [IF 2 THYRISTOR CHARACTERISTICS OFF GATE VOLTAGE OPERATION OF STARTING FUEL INJECTION SYSTEM QEF INVENTOR 8016-50 A 0 BY 9 g I l ATTO START-UP FUEL INJECTION SYSTEM This invention relates generally to a fuel injection system for an internal combustion engine and more particularly to a fuel injection system which is operative during start-up to enrich the air-fuel mixture at the starting in the case where the engine temperature is below a predetermined value.

As is well known, starting of an internal combustion engine can be remarkably facilitated by supplying a greater amount of fuel in a highly atomized form to the individual cylinders of the engine than that supplied during normal or steady-state operation. This is effective particularly during cold conditions such as in cold weather. For this purpose a conventional start-up fuel injection system employs a fuel injection nozzle capable of supplying fuel in a highly atomized form, which nozzle is energized by means comprising relays or transistor circuit. However, in such means using relays they tend to chatter, thus affecting the means adversely.

Use of the transistor circuit tends to render the operation of the solenoid valve mounted in the nozzle unreliable if the supply voltage thereto varies, since the output driving current of the transistor to drive the solenoid valve is not sufficient to be able to overcome the influence by the variation of the supply voltage.

It is therefore an object of this invention to provide a fuel injection system which is operative during start-up to increase the richness of the air-fuel mixture at the starting in the case where the engine temperature is below a'predetermined value.

It is another object of this invention to provide a start-up fuel injection system, as above, which has a controlled rectifier, such as, of a thyristor for closing and opening the circuit through a solenoid valve mounted in a nozzle.

It is a further object of this invention to provide a start-up fuel injection system, as above, which is simple in construction and has an increased reliability in operation.

In the drawings:

FIG. 1 is a schematic circuit diagram of a starting fuel injection system according to one embodiment of this invention;

FIG. 2 schematically shows the operation of a thyristor used as a switch in the start-up fuel injection system of FIG. 1; and

FIG. 3 schematically shows the relationship between the operation of the present start-up fuel injection system and the engine temperature.

Referring now to FIG. 1, a starting fuel injection system according to one embodiment of this invention is shown. In the figure, reference numeral designates a starting fuel injection nozzle which is adapted to supply fuel in a highly atomized form to the intake air to be delivered to an engine cylinder 11. The nozzle 10 is mounted on an intake manifold 12 just downstream of a throttle valve 13 mounted therein. While the nozzle 10 is shown as located in the intake manifold it is to be understood that the nozzle 10 could equally well be located to supply atomized full directly into the cylinder of the engine downstream of the intake valve. The nozzle 10 is opened and closed by a solenoid valve 14 which is energized by a control unit.

The control unit includes a thermistor 15 having a high temperature coefficient of resistance which is mounted on a cylinder block 16 of the engine so as to sense the engine temperature. The thermistor 15 has two terminals, one of which is grounded. The other terminal of the thermistor 15 is connected via a resistor 17 to the gate of a controlled rectifier, such as of a thyristor 18, the cathode thereof being grounded. The thyristor 18 has its anode grounded by way of a resistor 19 and a capacitor 20 which are connected in series to each other. The anode of the thyristor 18 is also connected to the coil 21 of the solenoid valve 14 which coil has a diode 22 connected thereacross. The solenoid coil 21 is connected via a resistor 23 and a starting switch 24 to a battery 25. Connected at a junction 26 between the resistor 23 and the starting switch 24 is a resistor 27 having one end connected to the thermistor 15.

In the operation of the embodiment shown in FIG. 1, when the starting switch 24 is closed for start-up operation, the potential at a point 28 between the resistor 27 and the thermistor 15 becomes to a level which is dependent upon the varying resistances of the thermistor 15. The potential at the point 28 is imposed on the gate of the thyristor 18 via the resistor 17. The resistance values of the resistors 17 and 27 and the thermistor 15 are adjusted so that when the engine temperature sensed by the thermistor 15 is below a predetermined value, such as, for example 20C, the potential at the point 28 is sufficiently high to turn on the thyristor 18. That is, when the engine temperature is below the predetermined value, the thermistor 15 represents so high a resistance that the potential at the point 28. is increased to render the thyristor l8 conductive. Conduction of the thyristor 18 makes the circuit through the solenoid coil 21 and the resistor 23 to energize the solenoid valve 14 during the duration of the starting switch 24 being closed. As a result the fuel nozzle 10 is operative to supply atomized fuel to the intake manifold 12 so as to enrich the air-fuel mixture, thereby facilitating to start the engine. Once the engine has been started, the starting switch 24 is opened to de-energize the control unit and the solenoid valve 14 in this sequence so that the fuel nozzle 10 ceases to inject fuel into the intake manifold 12.

FIG. 2 schematically shows the behaviors of the thyristor 18 in terms of the voltage imposed on the gate electrode. As will be seen there is a relatively large difference between the turn-on gate voltage and turn-off gate voltage of the thyristor, and further, when the gate voltage is raised up to the turn-on gate voltage, the anode current suddenly jumps from zero to a very high value. Therefore, the solenoid valve 14 which is kept open while the anode current flows therethrough operates to actuate the fuel nozzle 10 with increased reliability. In this type of fuel injection system, there occurs no chattering which is an inherent drawback in the systems employing relays.

FIG. 3 schematically shows the relationship between the operation of the start-up fuel injection system and the engine temperature. As shown in FIG. 3 and described above, this system is adapted to actuate the starting fuel injection valve 14 in the case where the engine temperature is below the predetermined value, such as 20C, while when the temperature is above the predetermined value the injection valve 14 is not actuated. More specifically, when the engine temperature is above the predetermined value, the thermistor 15 has so low a resistance thatthe potential appearing at the point 28 when the starting switch 24 is closed is not sufficiently high to render the thyristor 18 conductive. It is to be noted that the temperature point below which the solenoid valve 14 is actuated upon closure of the starting switch 24 can be varied by adjustment of the resistance values of the resistors 17 and 27 and the thermistor 15.

As has been described above, this invention provides a new and improved start-up fuel injection system having a controlled rectifier, such as of a thyristor, and which can inject fuel with increased reliability when the engine temperature is below a predetermined value.

What is claimed is:

l. A start-up fuel injection system for an internal combustion engine having an engine cylinder, a cylinder block and a fuel injection nozzle adapted to supply fuel in highly atomized form to intake air to be delivered to said engine cylinder when opened, said start-up fuel injection system comprising a battery; a starting switch connected to said battery; a solenoid valve for closing and opening said fuel injection nozzle; a solenoid coil having first and second terminals; said solenoid coil being connected at its first terminal to said battery through said starting switch; a thyristor having an anode connected to said second terminal of said solenoidcoil and a cathode; a first resistor connected at its one end to said cathode of said thyristor; a second resistor having one end connected to the other end of said first resistor and the other end connected to a junction between said first terminal of said solenoid coil and said starting switch, and a thermistor having a high temperature resistance mounted on said cylinder block and connected to a point between said first and second resistors, the resistance values of said first and second resistors and said thermistor being determined to cause the potential at the point between said first and second resistors to be high so as to turn on said thyristor when said engine temperature is below the predetermined value, said solenoid coil is energized to actuate said solenoid valve for thereby opening said starting fuel injection nozzle.

2. A start-up fuel injection nozzle according to claim 1, further comprising a resistor connected between said second terminal of said solenoid coil and said anode of said thyristor, and a capacitor having one terminal connected to said resistor and the other terminai connected to the ground.

3. A start-up fuel injection system according to claim 1, wherein said solenoid coil includes a diode connected across said first and second terminals at said solenoid coil. 

1. A start-up fuel injection system for an internal combustion engine having an engine cylinder, a cylinder block and a fuel injection nozzle adapted to supply fuel in highly atomized form to intake air to be delivered to said engine cylinder when opened, said start-up fuel injection system comprising a battery; a starting switch connected to said battery; a solenoid valve for closing and opening said fuel injection nozzle; a solenoid coil having first and second terminals; said solenoid coil being connected at its first terminal to said battery through said starting switch; a thyristor having an anode connected to said second terminal of said solenoid coil and a cathode; a first resistor connected at its one end to said cathode of said thyristor; a second resistor having one end connected to the other end of said first resistor and the other end connected to a junction between said first terminal of said solenoid coil and said starting switch, and a thermistor having a high temperature resistance mounted on said cylinder block and connected to a point between said first and second resistors, the resistance values of said first and second resistors and said thermistor being determined to cause the potential at the point between said first and second resistors to be high so as to turn on said thyristor when said engine temperature is below the predetermined value, said solenoid coil is energized to actuate said solenoid valve for thereby opening said starting fuel injection nozzle.
 2. A start-up fuel injection nozzle according to claim 1, further comprising a resistor connected between said second terminal of said solenoid coil and said anode of said thyristor, and a capacitor having one terminal connected to said resistor and the other terminal connected to the ground.
 3. A start-up fuel injection system according to claim 1, wherein said solenoid coil includes a diode connected across said first and second terminals at said solenoid coil. 